The present invention relates to a hydraulic system, in particular for motor vehicles, including a master cylinder, a slave cylinder, and a pressure medium line connecting these two, as well as a hydraulic valve, in particular for use in a hydraulic system for motor vehicles.
It is known that a servo-supported hydraulic system may be used for clutch operation to reduce the pedal force exerted by the driver of a motor vehicle. For example, an electric pump in the hydraulic system increases the pressure between the master cylinder and the slave cylinder. The pump may be electronically regulated, for example. To do so, at least one pressure sensor is required in the hydraulic system because the pump pressure is pressure dependent. One disadvantage of such systems is that the cost is relatively high (e.g., due to the pressure sensor and the electronic regulation), the hysteresis of the clutch characteristic is reproduced and sometimes even increased in the pedal force curve, in particular at high pedal speeds, and there may be additional pulsation of the pedal.
European Patent Application No. 00 412 711 (DE 690 09 345) describes a hydraulic system for a continuously variable transmission (CVT) in which multiple control valves are provided in the regulating circuits for the transmission adjustment and clutch control. The control valves are each triggered by their own electronically regulated hydraulic control circuits.